The invention relates to improvements in flexible pipe couplings of the type disclosed in commonly owned U.S. Pat. No. 4,616,858 granted Oct. 14, 1986.
The patent discloses a coupling wherein the split ring of the clamping means which is used to deform an elastic sleeve into sealing engagement with the end portions of pipes extending into the respective ends of the sleeve has a centrally located circumferential corrugation which extends into a circumferential groove in the external surface of the sleeve. The means for clamping the sleeve further comprises two projections which are disposed in the region of the split in the ring and can be pulled toward each other by a bolt and nut. An arcuate insert is provided to extend across the gap between the projections radially inwardly of the respective portion of the ring, and such insert has a corrugation which receives the corresponding portion of the corrugation of the ring. The sleeve has a centrally located internal partition which is disposed between the end faces of the pipes and is likely to be forced radially inwardly beyond the internal surfaces of the pipes in response to pronounced tensioning of the split ring. The radially innermost portion of the partition then interferes with the flow of material which is conveyed through the pipes. Such penetration of the partition radially inwardly beyond the internal surfaces of the pipes is especially likely to take place if the sleeve and the split ring are used to establish a coupling between two relatively thin-walled pipes.
The main sealing action between the sleeve and the pipes takes place in regions which are close to the end faces of the pipes. This can result in leakage in response to pronounced changes in orientation of the pipes, i.e., if the pipes are caused to move out of exact axial alignment with one another. A break in the sealing action of the coupling is particularly likely to occur if the sleeve surrounds the end portions of two large-diameter pipes and/or if the end faces of the pipes are not disposed in planes which extend exactly at right angles to the axes of the respective pipes. It has been found that the seal between the internal surface of the sleeve and the peripheral portions of the pipes is likely to be affected if the mutual inclination of the axes of the pipes is rather pronounced, if the diameters of the pipes are large and also if the planes of the end faces of the pipes are not exactly normal to the axes of the pipes; the leak is likely to develop in regions where the end faces of the mutually inclined pipes are disposed at a maximum distance from one another. In fact, the sleeve is prevented from establishing a requisite sealing engagement between its internal surface and the peripheral surfaces of the pipes right from the start if the pipes are not exactly coaxial at the time their end portions are introduced into the sleeve and the split ring is tensioned to deform the sleeve. Thus, the mutual inclination of the pipes can be sufficiently pronounced to move portions of their end faces far away from one another (i.e., the gap between the end faces will assume the shape of a pronounced Vee) whereby the peripheral surfaces of the pipes are remote from the region where the sleeve has undergone maximum compression and is expected to establish the main sealing action. The region of maximum compression is inwardly adjacent the single corrugation of the split ring. The ribs which are provided at the axial ends of the sleeve then constitute the only means for preventing escape of the confined flowable material and/or penetration of gases or other fluids from the surrounding atmosphere into the space between the end faces, and thence into the interior, of the pipes.
The coupling which is disclosed in the aforediscussed commonly owned Pat. No. 4,616,858 is somewhat similar to the coupling which is disclosed in commonly owned U.S. Pat. No. 4,627,645 granted Dec. 9, 1986.